MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Physics
8.02
Fall 2007
Turn in at your table during class labeled with your name and group (e.g. L02 12A)
Problem Set 8
Due: Wednesday, October 31
st
at class beginning (before 10:15/12:15)
This problem set focuses on material from classes 18-20 (week 8).
Textbook references
can be found at the top of the summaries from these three days.
Warm Up
Problem 1: Charges in a Uniform Field
An electron with velocity
ˆ
ˆ
x
y
v
v
+
i
j
moves through a uniform magnetic field
ˆ
ˆ
x
y
B
B
+
i
j
(a)
Find the magnitude of the force on the electron.
(b)
Repeat your calculation for a proton having the same velocity.
Problem 2: Power Line
A horizontal power line carries a current of
I
from south to north. Earth's magnetic field
(
B
Earth
= 62.1 μT) is directed toward the north and is inclined downward at an angle
θ
to
the horizontal. Find the magnitude of the magnetic force on a length
L
of the line due to
Earth's field.
Please also calculate a value numerically for
I
= 3000 A,
θ
= 78.0º and
L
=
100 m, since it’s useful to think about real world numbers.
Problem 3: Triangular Loop
A current loop, carrying a current
I
, is in the shape of a right triangle with sides 30, 40,
and 50 cm. The loop is in a uniform magnetic field
B
whose direction is parallel to the
current in the 50 cm side of the loop.
Find the magnitude of
(a)
the magnetic dipole moment of the loop in amperes-square meters; and
(b)
the torque on the loop.
PS08-1

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